The invention relates to clamping devices for releasably clamping an insertion member.
A common application of clamping devices is the releasable clamping of a cutting tool (constituting an insertion member) in a toolholder (constituting a clamping device). In JP Unexamined Patent Publication 7-9212, there is illustrated and described a side lock toolholder having an insertion bore formed by the union of an access bore portion and a gripping bore portion, the access bore portion and the gripping bore portion sharing a common longitudinal axis and respectively having, a radius rxe2x80x2 and a radius r where rxe2x80x2 greater than R greater than r and R is the radius of a cutting tool""s right circular cylindrical shank. The access bore portion extends over an arc angle of almost 180xc2x0 such that the cutting tool is freely slidingly insertable thereinto and withdrawable therefrom, the cutting tool being forcibly displaceable from the access bore portion to the gripping bore portion. Such a toolholder has a disadvantage that the arc angle of the gripping bore portion is less than 180xc2x0 which reduces the gripping capability of the gripping bore portion which impairs stability during a cutting operation.
In accordance with the present invention, there is provided a clamping device for releasably clamping an insertion member, the clamping device comprising a clamping member having an insertion bore formed by the union of an access bore portion and a gripping bore portion for the free sliding insertion into and withdrawal from of the shank portion in respect of said access bore portion and its clamping by a clamping surface of said gripping bore portion on its forced displacement thereinto from said access bore portion
characterized in
said access and gripping bore portions having longitudinal axes spaced apart at least along a portion thereof.
In accordance with a first mode of implementation of the present invention, an insertion bore can be formed by the union of a pair of circular cross section access and gripping bore portions respectively having longitudinal axes which are parallel and offset one from another whereby an insertion member is sideways forcibly displaced from its access bore portion to its gripping bore portion. Preferably, an access bore portion has a right circular cylindrical shape whilst a gripping bore portion can have either a right circular cylindrical shape or a right circular frusto-conical shape.
In accordance with a second mode of implementation of the present invention, an insertion bore can be formed by the union of a pair of circular cross section access and gripping bore portions respectively having longitudinal axes which are intersecting whereby an insertion member is pivotally forcibly displaced from its access bore portion into its gripping bore portion. Preferably, an access bore portion has an inclined circular cylindrical shape whilst an gripping bore portion has a right circular cylindrical shape.
In both modes of implementation, the access bore portion has a diameter D1 whose minimum value is greater than the diameter D0 of an insertion members shank portion whilst the gripping bore portion has a maximum value D2 which is less than D0. In addition, in the former mode of implementation, the two longitudinal axes are spaced apart at a distance D3 whilst in the latter mode of implementation, the two longitudinal axes are inclined at an inclination angle xcex3.